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xfrm: policy: prepare policy_bydst hash for rcu lookups
Since commit 56f047305d
("xfrm: add rcu grace period in xfrm_policy_destroy()") xfrm policy
objects are already free'd via rcu.
In order to make more places lockless (i.e. use rcu_read_lock instead of
grabbing read-side of policy rwlock) we only need to:
- use rcu_assign_pointer to store address of new hash table backend memory
- add rcu barrier so that freeing of old memory is delayed (expansion
and free happens from system workqueue, so synchronize_rcu is fine)
- use rcu_dereference to fetch current address of the hash table.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
parent
a5eefc1df6
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@ -385,9 +385,11 @@ static struct hlist_head *policy_hash_bysel(struct net *net,
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__get_hash_thresh(net, family, dir, &dbits, &sbits);
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hash = __sel_hash(sel, family, hmask, dbits, sbits);
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return (hash == hmask + 1 ?
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&net->xfrm.policy_inexact[dir] :
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net->xfrm.policy_bydst[dir].table + hash);
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if (hash == hmask + 1)
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return &net->xfrm.policy_inexact[dir];
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return rcu_dereference_check(net->xfrm.policy_bydst[dir].table,
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lockdep_is_held(&net->xfrm.xfrm_policy_lock)) + hash;
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}
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static struct hlist_head *policy_hash_direct(struct net *net,
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@ -403,7 +405,8 @@ static struct hlist_head *policy_hash_direct(struct net *net,
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__get_hash_thresh(net, family, dir, &dbits, &sbits);
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hash = __addr_hash(daddr, saddr, family, hmask, dbits, sbits);
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return net->xfrm.policy_bydst[dir].table + hash;
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return rcu_dereference_check(net->xfrm.policy_bydst[dir].table,
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lockdep_is_held(&net->xfrm.xfrm_policy_lock)) + hash;
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}
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static void xfrm_dst_hash_transfer(struct net *net,
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@ -468,8 +471,8 @@ static void xfrm_bydst_resize(struct net *net, int dir)
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unsigned int hmask = net->xfrm.policy_bydst[dir].hmask;
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unsigned int nhashmask = xfrm_new_hash_mask(hmask);
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unsigned int nsize = (nhashmask + 1) * sizeof(struct hlist_head);
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struct hlist_head *odst = net->xfrm.policy_bydst[dir].table;
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struct hlist_head *ndst = xfrm_hash_alloc(nsize);
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struct hlist_head *odst;
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int i;
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if (!ndst)
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@ -477,14 +480,19 @@ static void xfrm_bydst_resize(struct net *net, int dir)
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write_lock_bh(&net->xfrm.xfrm_policy_lock);
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odst = rcu_dereference_protected(net->xfrm.policy_bydst[dir].table,
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lockdep_is_held(&net->xfrm.xfrm_policy_lock));
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for (i = hmask; i >= 0; i--)
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xfrm_dst_hash_transfer(net, odst + i, ndst, nhashmask, dir);
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net->xfrm.policy_bydst[dir].table = ndst;
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rcu_assign_pointer(net->xfrm.policy_bydst[dir].table, ndst);
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net->xfrm.policy_bydst[dir].hmask = nhashmask;
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write_unlock_bh(&net->xfrm.xfrm_policy_lock);
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synchronize_rcu();
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xfrm_hash_free(odst, (hmask + 1) * sizeof(struct hlist_head));
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}
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